Estimation of joint incongruence in dysplastic canine elbows before and after dynamic proximal ulnar osteotomy.

Objective: To characterize joint incongruence in dysplastic canine elbows before and after dynamic proximal ulnar osteotomy (DPUO).

Study Design: Clinical, prospective study.

Animals: Dogs (n = 10; 12 elbows) with ≥ 2 mm radioulnar incongruence (RUI), FCP, and/or OCD.

Methods: Computed tomography in a nonload bearing position was used to generate in silico 3D models of the elbow joint before DPUO, and this was repeated after DPUO union (median 3 months postoperatively). On these models, RUI, humeroradial and humeroulnar subchondral joint space width (SJSW) as well as alignment of the proximal ulnar segment were investigated.

Results: RUI at the medial coronoid process (MCP) decreased (P = .001), while it increased at the lateral coronoid process (P = .0005), and remained unchanged at the level of the trochlear ridge (P = .25). SJSW at the MCP increased (P = .001), changing from focal joint space collapse preoperatively to a more homogeneous pattern of moderate SJSW at follow-up. The proximal ulnar segment rotated in all 3 planes with caudal tipping at the level of the osteotomy and varus deformity, while no axial translation could be noted.

Conclusions: DPUO results in reduction of RUI and amelioration of focal contact area at the MCP. This effect is the result of a complex three-dimensional rotation of the proximal ulnar segment, rather than axial shift.